Methods and devices for tracking objects by surgical navigation systems

ABSTRACT

A method and device for tracking objects by surgical navigation systems. The method includes: capturing an image of the tracked object; determining whether a unique identifiable feature associated with at least one totem pattern is discernible in the image; when the unique identifiable feature is discernible: determining a position or an orientation of the tracked object based on the at least one totem pattern; and registering the at least one totem pattern in the surgical coordinate space; and when the unique identifiable feature is indiscernible: determining a position of each totem pattern relative to other totem patterns such that a combination of totem patterns within the captured image is a marker group detectable as a composite totem pattern; determining a position or an orientation of the tracked object based on the composite totem pattern associated with the tracked object; and registering the composite totem pattern in the surgical coordinate space.

FIELD

The present application generally relates to surgical navigation systemsand, in particular, to methods and devices for tracking objects.

BACKGROUND

Surgical navigation systems may include optical imaging devices fordetecting objects within a surgical navigation space. The surgicalnavigation systems may rely on reference markers for identifying trackedobjects and for determining position or orientation of the trackedobject. When the position or the orientation of a tracked object isdetermined, surgical navigation systems may register captured images ina prescribed coordinate space such that the captured image data may becompared or integrated with other data for presentation on a commondisplay device.

BRIEF SUMMARY

In one aspect, the present application describes a method of tracking anobject in a surgical coordinate space by a surgical navigation systemincluding an optical imaging device, the tracked object having areference body affixed thereto, the reference body comprising asubstrate and a first layer affixed to the substrate, the first layerincluding a plurality of totem patterns, each totem pattern having aunique identifiable feature distinguishing that totem pattern fromanother totem pattern in the plurality of totem patterns. The methodincludes capturing an image of the tracked object, the image includingimage data associated with at least one totem pattern; determiningwhether a unique identifiable feature associated with at least one totempattern is discernible in the image; when the unique identifiablefeature associated with at least one totem pattern is discernible:determining a position or an orientation of the tracked object in thesurgical coordinate space based on the at least one totem pattern; andregistering the at least one totem pattern associated with the trackedobject in the surgical coordinate space; and when the uniqueidentifiable feature associated with at least one totem pattern isindiscernible: determining a position of each totem pattern relative toother totem patterns in the captured image such that a combination oftotem patterns within the captured image is a marker group detectable bythe surgical navigation system as a composite totem pattern; determininga position or an orientation of the tracked object in the surgicalcoordinate space based on the composite totem pattern associated withthe tracked object; and registering the composite totem patternassociated with the tracked object in the surgical coordinate space.

In another aspect, the present application describes a reference bodyaffixable to objects tracked by a surgical navigation system. Thereference body includes: a substrate having a substrate surface area; afirst layer affixed to the substrate, the first layer including a firsttotem pattern at a first position centered at an origin of orientationaxes, the first totem pattern including a unique identifiable featuredistinguishing the first totem pattern from another totem pattern; and aretroreflective portion affixed to the substrate at a second positionfrom the origin position, wherein the retroreflective portion isdetectable by an optical imaging device of the surgical navigationsystem for determining position information of the reference body in asurgical navigation coordinate space.

In another aspect, the present application describes a reference bodyaffixable to objects tracked by a surgical navigation system. Thereference body includes: a substrate; a first layer affixed to thesubstrate, the first layer including a first totem pattern at a firstposition centered at an origin of orientation axes, the first totempattern including a unique identifiable feature distinguishing the firsttotem pattern from another totem pattern; and at least one touchpointdivot for touch point registration of the first totem pattern, the atleast one touchpoint divot being a through-hole in the first layer andbeing associated with the first totem pattern, the at least onetouchpoint divot being positioned at a respective known distance fromthe origin.

In another aspect, the present application describes a surgicalnavigation system to track an object in a surgical coordinate space, thetracked object having a reference body affixed thereto, the referencebody comprising a substrate and a first layer affixed to the substrate,the first layer including a plurality of totem patterns, each totempattern having a unique identifiable feature distinguishing that totempattern from another totem pattern in the plurality of totem patterns.The surgical navigation system includes: a processor; an optical imagingdevice coupled to the processor; and a memory coupled to the processorand storing processor-readable instructions that, when executed, causethe processor to: capture an image of the tracked object, the imageincluding image data associated with at least one totem pattern;determine whether a unique identifiable feature associated with at leastone totem pattern is discernible in the image; when the uniqueidentifiable feature associated with at least one totem pattern isdiscernible: determine a position or an orientation of the trackedobject in the surgical coordinate space based on the at least one totempattern; and register the at least one totem pattern associated with thetracked object in the surgical coordinate space; and when the uniqueidentifiable feature associated with at least one totem pattern isindiscernible: determine a position of each totem pattern relative toother totem patterns in the captured image such that a combination oftotem patterns within the captured image is a marker group detectable bythe surgical navigation system as a composite totem pattern; determine aposition or an orientation of the tracked object in the surgicalcoordinate space based on the composite totem pattern associated withthe tracked object; and register the composite totem pattern associatedwith the tracked object in the surgical coordinate space.

In another aspect, the present application describes processor-readableinstructions that, when executed, configure a processor to perform oneor more of the operations described herein. In this respect, the termprocessor is intended to include all types of processing circuits orchips capable of executing program instructions.

Other aspects and features of the present application will be understoodby those of ordinary skill in the art from a review of the followingdescription of examples in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example, to the accompanyingdrawings which show example embodiments of the present application.

FIG. 1 illustrates a perspective view of a surgical navigation system,in accordance with an example of the present application;

FIG. 2 illustrates further components of the surgical navigation systemof FIG. 1, in accordance with an example of the present application;

FIG. 3 illustrates a perspective view of an augmented reality device, inaccordance with an example of the present application;

FIG. 4 illustrates a block diagram of the augmented reality device ofFIG. 3, in accordance with an example of the present application;

FIG. 5 illustrates an augmented reality device configured to operatewith a surgical navigation system within an operating room environmentfor a port-based surgical procedure, in accordance with an example ofthe present application;

FIG. 6A illustrates a reference body 600 affixable to objects tracked bya surgical navigation system, in accordance with an example of thepresent application;

FIG. 6B illustrates an exploded perspective view of the reference body600 of FIG. 6A;

FIG. 7 illustrates a reference body 700 affixable to objects tracked bya surgical navigation system, in accordance with another example of thepresent application;

FIG. 8 illustrates a reference body 800 affixable to objects tracked bya surgical navigation system, in accordance with another example of thepresent application;

FIG. 9 illustrates a reference body 900 including a plurality ofuniquely identifiable totem patterns, in accordance with an example ofthe present application;

FIG. 10 illustrates a flowchart of a method of tracking an object in asurgical coordinate space by a surgical navigation system, in accordancewith an example of the present application;

FIG. 11 illustrates example totem patterns, in accordance with examplesof the present application; and

FIG. 12 illustrates example totem patterns, in accordance with examplesof the present application.

Similar reference numerals may have been used in different figures todenote similar components.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Various examples and aspects of the present application will bedescribed with reference to the details discussed below. The followingdescription and drawings are illustrative of the present application andare not to be construed as limiting the present application. Numerousdetails are described to provide a thorough understanding of variousembodiments. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofthe embodiments of the present application.

As used herein, the terms “comprises” and “comprising” are to beconstrued as being inclusive and open ended, and not exclusive.Specifically, when used in the specification and claims, the terms“comprises” and “comprising” and variations thereof mean the specifiedfeatures, steps, or components are included. These terms are not to beinterpreted to exclude the presence of other features, steps, orcomponents.

As used herein, the term “exemplary” means “serving as an example,instance, or illustration”, and should not be construed as preferred oradvantageous over other configurations disclosed herein.

As used herein, the terms “about”, “approximately”, and “substantially”are meant to cover variations that may exist in the upper and lowerlimits of the ranges of values, such as variations in properties,parameters, and dimensions. In a non-limiting example, the terms“about”, “approximately”, and “substantially” may mean plus or minus 10percent or less.

As used herein, the phrase “intraoperative” refers to an action,process, method, event or step that occurs or is carried out during atleast a portion of a medical procedure. Intraoperative, as definedherein, is not limited to surgical procedures, and may refer to othertypes of medical procedures.

In the present application, the term “and/or” is intended to cover allpossible combination and sub-combinations of the listed elements,including any one of the listed elements alone, any sub-combination, orall of the elements, and without necessarily excluding additionalelements.

In the present application, the phrase “at least one of . . . or . . . ”is intended to cover any one or more of the listed elements, includingany one of the listed elements alone, any sub-combination, or all of theelements, without necessarily excluding any additional elements, andwithout necessarily requiring all of the elements.

The term “registration” or the expression “image registration” refers tothe process of determining a transform to be used in correlating pointsacross different coordinate systems. For example, the term registrationmay refer to determining a transform for correlating three-dimensionalpoints across Cartesian coordinate systems. For example, registrationmay link points in a navigation coordinate space to an image coordinatespace such that data positioned in one coordinate system may be mappedto another coordinate system using the transform. Data may includephotographs, data from different sensors, times depths, or viewpoints.The process of registration is used in some examples for medical imagingin which images from different imaging modalities are co-registered.Registration may be utilized to compare or integrate data obtained fromdifferent modalities for presentation on a common platform or display.

It will be appreciated that there may be numerous registrationtechniques and one or more of the registration techniques may be appliedto examples of the present application. Non-limiting examples includeintensity-based methods that may compare intensity patterns in imagesvia correlation metrics. Feature-based methods may identifycorrespondence between image features such as points, lines, andcontours. Image registration methods may be classified according totransformation models used to relate a target image space to a referenceimage space. Classifications may be made between single-modality andmulti-modality methods. Single-modality registration methods mayregister images in the same modality acquired by the same scanner orsensor type. For example, a series of magnetic resonance (MR) images maybe co-registered. Multi-modality registration methods may be used toregister images acquired by different scanner or sensor types. Forexample multi-modality registration methods may register an imageobtained with magnetic resonance imaging (MRI) technology with an imageobtained with positron emission tomography (PET) technology.Multi-modality registration methods may be used, for example, withmedical imaging of the head and/or brain, the spine, or other portionsof a patient, where images of the patient may commonly be obtained fromdifferent types of scanners or imaging devices. For example,registration may correlate computerized tomography (CT) and MRI images,or may correlate PET and CT images for tumor localization, or maycorrelate contrast-enhanced CT images with non-contrast-enhanced CTimages, or may correlate ultrasound images with CT images.

In some examples, surgical navigation systems may identify trackedobjects or determine position and/or orientation of a tracked objectbased on an individual reference marker. Detection of a reference markermay include visual detection by an optical imaging device. Referencemarkers can include identifiable symbols, patterns, text, an arrangementof marks within a unique pattern, or the like. For example, referencemarkers may be known as totems or totem patterns. Surgical navigationsystems may also identify markers and determine position or orientationof tracked objects based on a combination of discrete reference markersspatially arranged in a pre-determined configuration.

However, surgical navigation systems depending on visual detection ofreference markers may encounter challenges in numerous scenarios,including when: (1) reference markers are visually imperceptible withincaptured images (e.g., reference markers in captured images are out offocus or are too small to discern); or (2) a subset of reference markersin a combination of spatially arranged reference markers for determiningposition or orientation are not captured within captured images. It maybe desirable to provide methods, devices, or systems to addresschallenges when visually detecting or tracking objects using a surgicalnavigation system.

In an aspect, the present application provides a method of tracking anobject in a surgical coordinate space, where the tracked object mayinclude a reference body affixed thereto. The reference body may includea substrate and a first layer affixed to the substrate. The first layermay include a plurality of totem patterns. Each totem pattern may have aunique identifiable feature distinguishing that totem pattern fromanother totem pattern in the plurality of totem patterns. A position ofeach totem pattern relative to other totem patters in the plurality oftotem patterns may be pre-configured or pre-arranged. The method mayinclude capturing an image of the tracked object and determining whethera unique identifiable feature associated with at least one totem patternis discernible in the image. Further, when the unique identifiablefeature of at least one totem pattern is discernible, the method mayinclude determining a position or an orientation of the tracked objectin the surgical coordinate space based on the at least one totempattern. Further, when the unique identifiable feature of at least onetotem pattern is indiscernible, the method may include determining aposition of each totem pattern relative to other totem patterns in thecaptured image such that a combination of totem patterns is a markergroup detectable as a composite totem pattern and determining a positionor an orientation of the tracked object based on the composite totempattern associated with the tracked object.

Reference is now made to FIG. 1, which illustrates a perspective view ofa surgical navigation system 200. The surgical navigation system 200 maybe positioned in an operating room (OR) for guiding a medicalprofessional conducting a surgical procedure. In the example illustratedin FIG. 1, the medical professional 101 may conduct a minimally-invasiveaccess port based surgical procedure on a patient 102 in the ORenvironment. The surgery may be in the field of neurosurgery and themedical professional 101 may be positioned adjacent a head of thepatient 102. Although the OR environment illustrated in FIG. 1 is setupfor conducting a neurosurgical procedure, in some other examples, the ORenvironment may be setup for other types of medical procedures, such asspinal surgery.

In addition to the surgical navigation system 200, the OR environmentmay include other equipment, such as surgical tool trays, carts, andbooms. Some example equipment may include surgical lights, oxygen orother gas supplies, anesthesia supplies, etc.

Reference is now made to FIG. 2 which illustrates further components ofthe surgical navigation system 200 of FIG. 1, in accordance with anexample of the present application. The surgical navigation system 200may include an equipment tower 201, a tracking system 213, and at leastone display device, such as a primary display device 211 and a secondarydisplay device 205. The tracking system 213 may include optical imagingdevices, such as cameras. In the example illustrated in FIG. 2, thetracking system 213 may include two laterally spaced-apart cameras forstereoscopic image capture. The cameras may be three-dimensional (3D)optical tracking stereo cameras, such as Northern Digital Imaging® (NDI)optical tracking stereo cameras. The surgical navigation system 200 maybe configured to track at least one instrument, such as an access port206, for assisting a medical professional 101 (FIG. 1) during a surgicalprocedure.

The surgical navigation system 200 may also include a device positioningunit 220. The device positioning unit 220 may include a robotic arm 202that supports an optical device, such as an optical scope 204 or camera.The optical scope 204 may be positioned in line with a trajectory ofaccess (co-axial with the access port 206) to enable the medicalprofessional 101 (FIG. 1) to have visual sight through the access port206. In examples where the optical scope 204 may include an imagesensor, such as a camera, images from the optical scope 204 may bedisplayed on at least one of the primary display device 211 or thesecondary display device 205. In some examples, the view or visual sightthrough the access port 206 may be integrated with other data, includingpre-surgical plan information or pre-surgical imaging information (e.g.,MRI, CAT scan, or ultrasound imaging information), and the addedinformation may be registered based on registration of the patient 102(FIG. 1) in the OR environment and/or registration of equipment relativeto the patient 102. The surgical navigation system 200 may also tracksurgical instruments, such as the access port 206 or other tools in theOR environment. The surgical navigation system 200 may map models of thesurgical instruments to a virtual space to which patient data may bemapped for rendering a combined display of the surgical instruments andthe patient data and/or pre-surgical imaging data on at least one of theprimary display device 211 or the secondary display device 205.

The equipment tower 201 may be mountable on a frame, such as a rack or acart. The equipment tower 201 may be configured to accommodate, forexample, a computer including a non-transitory, computer-readablestorage medium comprising processor-executable instructions and aprocessor executing the processor-executable instructions. Theprocessor-executable instructions may include, for example, surgicalplanning instructions, navigation instructions, robot controlinstructions, or any other types of instructions. The equipment towermay include other devices or components, such as power supplies, displaypanels, or printing devices.

In some examples, the surgical navigation system 200 may include apatient head mount 217 for retaining the patient in a position. Forexample, during a craniotomy procedure, a dura flap may be formed andretracted and the access port 206 may be inserted into the skull regionof the patient. The tracking system 213 may track and determine locationdata of one or more equipment or objects in the OR environment. Forexample, the tracking system 213 may track, in real-time, a robotic arm202 or surgical equipment, such as the access port 206. In someexamples, tracked equipment may include at least one reference marker orfiducial marker 212 affixed thereto. For example, the fiducial marker212 may be affixed to the access port 206 for tracking any movement, ifany, of the access port 206 and for tracking objects moving within thevicinity of the access port 206.

The secondary display device 205 may be configured to display real-timeinformation of the surgical navigation system 200. The displayedinformation may include multiple views of an instrument or of a portionof the patient. For example, the displayed information may include axialviews, sagittal views, coronal views, or other types of views ofinstruments or portions of the patient.

In some examples, the fiducial marker 212 may include reflective spheresdetectable by the tracking system 213, and the tracking system 213 maybe an optical imaging device. For example, the tracking system 213 maydetect electromagnetic emissions and the fiducial marker 212 may be anelectromagnetic-based marker. The tracking system 213 may track aposition of the fiducial marker 212 in a three-dimensional coordinatespace, and the surgical navigation system 200 may be configured tocorrelate the position to a virtual coordinate space, therebypositioning a model of a tracked instrument in a virtual coordinatespace.

Other types of fiducial markers, such as radio-frequency (RF),electromagnetic (EM), or light emitting diode (LED) (pulsed andun-pulsed) markers may be used. RF or EM markers may include specificsignatures for uniquely identifying specific tools. In other examples,fiducial markers may include glass spheres, reflective stickers, orother unique structures and patterns. In some examples, reflectivestickers, glass spheres, or LED markers may be detected using opticaldetectors, while RF or EM makers may be detected using antennadetectors.

In some examples, augmented reality (AR) systems and virtual realitysystems may be incorporated with surgical navigation systems. Augmentedreality systems may include an augmented reality device, headset, orglasses-like structure that allows a wearer to observe real worldobjects supplemented with additional rendered images on a lens of theaugmented reality device, headset, or glasses-like structure.Accordingly, augmented reality devices may be integrated with surgicalnavigation systems to provide additional information to a medicalprofessional. That is, augmented reality devices may augment the medicalprofessional's real world view of a patient or objects with imaging datasuch as pre-operative imaging data, surgical instrument models,real-time patient vital information, and/or pre-operative planinformation.

Reference is now made to FIG. 3, which illustrates a perspective view ofan augmented reality device 10, in accordance with an example of thepresent application. The augmented reality device 10 may include atransparent or near transparent display screen configured adjacent auser's eye(s) such that the augmented reality device 10 may provide afield of view through the display screen. The augmented reality device10 may be configured to display objects on the display screen to augmenta user's view of the real world. For example, the augmented realitydevice 10 illustrated in FIG. 3 may be configured as a pair of glasseswith a left display/lens 12, a right display/lens 14, and a pair of arms16 for fitting over the top and back of the user's ears. In someexamples, the augmented reality device 10 may include the leftdisplay/lens 12 and the right display/lens 14 for displaying pairs ofstereoscopic images for creating or enhancing the illusion of depth inthe pairs of stereoscopic images.

Reference is now made to FIG. 4, which illustrates a block diagram ofthe augmented reality device 10 of FIG. 3, in accordance with an exampleof the present application. The augmented reality device 10 may includea processor 30, memory 32, a left display/lens 12, and a rightdisplay/lens 14. The left display/lens 12 and the right display/lens 14may be integrated with transparent or semi-transparent lenses or visorsthrough which a user, who may be wearing the augmented reality device10, may view the real world. Images being displayed on the leftdisplay/lens 12 and the right display/lens 14 may be displayed withinthe user's field of view or line-of-sight of the real world.

The augmented reality device 10 may include orientation sensors 20 fortracking or determining changes in position and/or orientation of theaugmented reality device 10 in a coordinate system associated with thereal world. The augmented reality device 100 may be configured todisplay images in the left display/lens 12 or the right display/lens 14according to changes to the user's field of view or line-of-sight of thereal world through the left display/lens 12 or the right display/lens14, such that images displayed concurrent with the user's view of thereal world may appear as if they were positioned in the real world. Theorientation sensors 20 may include at least one of accelerometers,gyroscopes, proximity sensors, or any other sensors or devices forproviding position or orientation information relating to the augmentedreality device 10.

The augmented reality device 10 may include a camera 18 (or multiplecameras). The camera 18 may be oriented in substantially the samedirection as the field of view when the augmented reality device 10 isworn by the user. The camera 18 may be configured for identifyingobjects in the field of view of the augmented reality device 10 and forcorrelating or registering the identified objects in an augmentedreality coordinate space or any other coordinate space. The camera 18may also be configured for gesture recognition or other user inputfunctions.

The augmented reality device 10 may also include a communicationsubsystem 34. The communication subsystem 34 may be a wirelesscommunication subsystem and may be configured for enabling the augmentedreality device 10 to communicate with remote systems or remote computingdevices. In some examples, the communication subsystem 34 maycommunicate with a handheld device for receiving user input. Someexamples of handheld devices may include a wand for gesture input, amobile device, a smartwatch, a keyboard, a mouse, or the like. In someexamples, the communication subsystem 34 may enable communications withremote computing devices, including computing servers. In some examples,the communication subsystem 34 may communicate with computing devicessuch as a surgical navigation system 200 (FIG. 2) in an operating roomenvironment. Example communication protocols may include IEEE 802.11(WiFi), Bluetooth™, near field communication protocols, ZigBee™, or anyother suitable type of communication protocols.

The augmented reality device 10 may be configured to be worn likeglasses or a headset by a user. The examples components described abovemay be incorporated into the augmented reality device 10 or may bepartially enclosed in a nearby computing device and coupled to theaugmented reality device 10 via a wired or wireless communication link.Description of other components of the example augmented reality device10 have been omitted for ease of exposition and for clarity, includingcomponents such as power supplies, battery sources, other electroniccircuitry, etc.

In some examples, the augmented reality device 10 may overlaypre-operative scan data on the medical professional's view of thereal-world patient such that the medical professional may viewthree-dimensional CT scan data aligned with a patient's head. In anotherexample, the augmented reality device 10 may render “dashboard”information, such as patient vitals or other monitored data, such thatthe medical professional may view the dashboard information in themedical professional's peripheral vision while performing the medicalprocedure. For example, the augmented reality device 10 may maintainrendering of the dashboard information in the medical professional'sfield of view irrespective of what direction the augmented realitydevice 10 may be oriented towards. In another example, the augmentedreality device 10 may render pre-operative plan information, such ascraniometrical cut-lines for opening access to a skull, so as to guidethe medical professional during the surgical procedure. It may beappreciated from the description herein that a range of other possibleinformation may be displayed by an augmented reality device 10 to assistthe medical professional with planning, testing, practicing, orperforming medical procedures.

Reference is now made to FIG. 5, which illustrates an augmented realitydevice 10 configured to operate with a surgical navigation system withinan operating room environment for a port-based surgical procedure, inaccordance with an example of the present application. Although thesurgical navigation system and the augmented reality device 10 isillustrated for use during an access-port surgical procedure, thesurgical navigation system may be setup for other types of procedures,including spinal procedures, heart procedures, or any other type ofprocedure. In the illustrated example, a medical professional may beresecting a tumor or other tissue from a brain of a patient 502 throughan access port 506. In some examples, an external scope may be coupledto a robotic or positioning arm, and the external scope may beconfigured to allow the medical professional to view a magnified view oftissue through an opening of the access port 506. Images may be capturedby the external scope and may be displayed on a visual display, such asa display device mounted adjacent or in close proximity to the medicalprofessional. The medical professional may utilize displayed images onthe display device to view the surgical site. However, with such anenvironment, the medical professional may need to view displayed imageson the display device thereby shifting visual focus from the patient ormedical procedure site to the display device.

Thus, the medical professional 501 may wear the augmented reality device10 and the augmented reality device 10 may provide the medicalprofessional with a convenient method for augmenting the medicalprofessional's real world view with display data. For example, thedisplay data may be provided or rendered on the left display/lens 12and/or the right display/lens 14 (FIG. 4) and may include pre-operativescan data, a model of surgical instruments, patient vital information,and/or pre-operative plan information.

Active or passive fiducial markers 507, such as spherical markers, maybe arranged in a fixed geometrical arrangement in fixed relation toportions of a patient, a surgical site, surgical instruments, or objectswithin a surgical navigation environment. Accordingly, a trackingdevice, such as an optical imaging device, may detect the active orpassive fiducial markers 507 such that position and/or orientationinformation of objects associated with the active or passive fiducialmarkers 507 may be determined.

Reference is now made to FIG. 6A, which illustrates a reference body 600affixable to an object tracked by a surgical navigation system, inaccordance with an example of the present application. Simultaneousreference will be made to FIG. 6B, which illustrates an explodedperspective view of the reference body 600 of FIG. 6A, for highlightingfeatures described herein.

As illustrated in FIG. 6B, the reference body 600 may include asubstrate 610 having a substrate surface area. The substrate surfacearea may be defined by a length 612 and a width 614 of the substrate610. The substrate may be constructed of any rigid, flexible, orsemi-flexible material suitable for being affixed to objects tracked bythe surgical navigation system. For example, the substrate may be asticker backing material such that one surface of the substrate mayinclude adhesive material for adhering the sticker backing material toobjects being tracked. The substrate may be constructed of any othermaterials for supporting the reference body 600 having featuresdescribed herein.

The reference body 600 may include a first layer 620 affixed to thesubstrate 610. The first layer 620 may include a first totem pattern 622at a first position centered at an origin 624 of orientation axes 626.For example, the orientation axes 626 may be an x-axis and a y-axis of aCartesian coordinate system. Although the first totem pattern 622illustrated in FIG. 6A is centered at the origin 624 of orientation axes626, the first totem pattern 622 may be positioned at any other positionon the first layer 620 and have a pre-configured or pre-determinedposition identifiable relative to the origin 624.

The first totem pattern 622 may include one or more unique identifiablefeatures distinguishing the first totem pattern 622 from another totempattern. As will be illustrated in the present application, the firsttotem pattern 622 and other totem patterns may include uniqueidentifying features such as bar codes, unique symbols or designs, orthe like for differentiating that totem pattern from other totempatterns. In some examples, when the tracking system 213 (FIG. 2) of thesurgical navigation system 200 (FIG. 2) includes an optical imagingdevice, the first totem pattern 622 and other totem patterns may includeoptically detectable features that may uniquely identify that totempattern from other totem patterns.

The reference body 600 may also include a retroreflective portion 630affixed to the substrate at a second position from the origin 624. Theretroreflective portion 630 may include a surface that may reflect lightback to a light source such that the reflected light may be minimallyscattered. For example, the retroreflective portion 630 may reflectlight rays back along a light ray direction that is parallel to butopposite in direction than light transmitted from the light ray source.For example, the tracking system 213 may emit infrared light in adirection towards the retroreflective portion 630 and theretroreflective portion 630 may reflect the incident infrared light backto the optical imaging device in a direction that is parallel to butopposite to the direction of the incident infrared light. Accordingly,the retroreflective portion 630 of the reference body 600 may bedetectable by the tracking system 213 and the surgical navigation system200 may determine position information of the reference body 600 basedon the detection of the retroreflective portion 630 of the referencebody 600. That is, the surgical navigation system 200 may determine theposition of the tracked object by determining the position based onelectromagnetic reflection from respective retroreflective portionsbeing detected by the optical imaging device.

In some examples, the surgical navigation system 200 may determine theposition of the tracked object by determining the position based onelectromagnetic emissions from respective retroreflective portions beingdetected by the optical imaging device. The retroreflective portion 630may include active electromagnetic emitters and the retroreflectiveportion 630 may emit, for example, infrared light that may be detectedby the optical imaging device.

In some scenarios, it may be challenging to accurately position aretroreflective portion 630 at known or pre-configured positions fromthe origin 624. That is, it may be incrementally costly to employprecise pick-and-place operations for accurately placing retroreflectiveportions 630 at known positions from the origin 624. Manufacturingoperations for cutting through-holes or other through-shapes inmaterials, however, may be less challenging and less expensive ascompared to pick-and-place operations. Thus, in some examples, the firstlayer 620 may also include a first through-hole 632 associated with thefirst totem pattern 622 such that the retroreflective portion 630 may bedetectable by the surgical navigation system 200 subject to positioningof the first through-hole 632.

For example, the first through-hole 632 may be centered at the secondposition from the origin 624. That is, the first through-hole 632 may beat a pre-configured or known position from the origin 624 of theorientation axes 626. Further, the retroreflective portion 630 may beaffixed between the substrate 610 and the first layer 620 such that theretroreflective portion 630 is detectable by the tracking system 213(e.g., optical imaging device) via the first through-hole 632. Thecombination of the first layer 620 having the first through-hole 632,the retroreflective portion 630, and the substrate 610 provides a“retroreflective disk” detectable by the surgical navigation system.

In some examples, the surface area of the retroreflective portion 630may be less than the substrate surface area. As illustrated in FIG. 6B,the retroreflective portion 630 may be a rectangular strip ofretroreflective material, and the surface area of the retroreflectiveportion 630 may be less than the substrate surface area. Further, thesurface area of the retroreflective portion 630 may be greater than anarea of the first through-hole 632. For example, because the firstthrough-hole 632 may have a circular shape, the first through-hole 632may have a circular area, where the circular area may be less than thesurface area of the retroreflective portion 630. Because the surfacearea of the retroreflective portion 630 may be greater than the area ofthe first through-hole 632 and because the first through-hole 632 ispositioned adjacent the retroreflective portion 630, a subset of theretroreflective portion 630 may be detectable by the tracking system213, such as an optical imaging device, via the first through-hole 632.Thus, it may be appreciated that the retroreflective portion 630 may beplaced relatively coarsely between the first layer 620 and the substrate610, yet exposing the retroreflective portion 630 as a retroreflectivedisk to the surgical navigation system via the first through-hole 632results in an accurate pre-configured positioning of the retroreflectivedisk relative to the origin 624.

It will be appreciated that, in some examples, the surgical navigationsystem 200 may determine position information of the reference body 600in the surgical coordinate space based on the first totem pattern 622 orthe retroreflective disk. That is, position information may be deducedbased on detected markers. However, the surgical navigation system 200may be unable to determine orientation of the reference body 600 in thesurgical coordinate space based solely on the first totem pattern 622and the retroreflective portion 630 exposed via the first through-hole632. To determine orientation of the reference body 600, a greaternumber of reference points may be required.

Although the above example describes providing a “retroreflective disk”based on the combination of the first layer 620 having the firstthrough-hole 632, the retroreflective portion 630, and the substrate610, in some other examples, the retroreflective portion may be providedas a circular-shape and may be adhered to the surface of the first layerat the second position such that the retroreflective disk may bedetectable by the surgical navigation system. Further, in some examples,the reference body 600 may be configured not to include anyretroreflective portion or any retroreflective disks and may include oneor more totem patterns positioned on the first layer 620 withoutretroreflective disks.

Reference is now made to FIG. 7, which illustrates a reference body 700affixable to objects tracked by a surgical navigation system, inaccordance with another example of the present application. Thereference body 700 may include a first totem pattern 722 at a firstposition centered at an origin 724 of orientation axes 726. For example,the orientation axes 726 may be an x-axis and a y-axis of a Cartesiancoordinate system. Although the first totem pattern 722 illustrated inFIG. 7 is centered at the origin 724 of orientation axes 726, the firsttotem pattern 722 may be positioned at any other position on first layerof the reference body 700, having a pre-configured or pre-determinedposition identifiable relative to the origin 724. Further, although theorientation axes 726 may be associated with a Cartesian coordinatesystem, in some examples, the orientation axes 726 may be any othercoordinate system. It may be appreciated that the first totem pattern722 and the origin 724 of orientation axes 726 of FIG. 7 may be similarto the first totem pattern 622 and the origin 624 of orientation axes626 illustrated in FIGS. 6A and 6B.

In some examples, three or more marks may be required to uniquelyidentify objects, and four or more marks may be required to identify apose, such as position and/or orientation, of objects to which marks maybe associated. Thus, in some examples, the reference body 700 mayinclude a first layer having three or more through-holes associated withthe first totem pattern 722, where each of the three or morethrough-holes may be positioned at a respective known position ordistance from the origin 724 of orientation axes 726. For example, thereference body 700 may include the first layer having a firstthrough-hole 732, a second through-hole 734, and a third through-hole736. Each of the first through-hole 732, the second through-hole 734,and the third through-hole 736 may be positioned at a pre-configured orknown position relative to the origin 724.

The reference body 700 may also include a retroreflective portion (notexplicitly illustrated) affixed between the substrate and the firstlayer such that the retroreflective portion may be detectable by atracking system 213 (FIG. 2), such as an optical imaging device, viaeach of the three or more through-holes. The tracking system 213 maydetect each of the three or more through-holes as retroreflective disksfor determining a pose of the reference body 700 in the surgicalcoordinate space.

Although examples described herein include may retroreflective portionsdetectable by tracking systems 213 based on incident and reflectedelectromagnetic emissions (e.g., infrared light, visible light, or otherforms of electromagnetic radiation), other forms of markers may beincluded at known positions associated with the first through-hole 732,the second through-hole 734, and the third through-hole 736. Forexample, electromagnetic coils or touchpoint divots may be provided atthe first through-hole 732, the second through-hole 734, and the thirdthrough-hole 736 locations.

For example, a reference body may include a substrate and a first layeraffixed to the substrate. The first layer may include a first totempattern at a first position centered at an origin of orientation axes.The first totem pattern may include a unique identifiable featuredistinguishing the first totem pattern from another totem pattern. Thereference body may also include at least one touch point divot for touchpoint registration of the first totem pattern. The at least onetouchpoint divot may be a through-hole in the first layer and may beassociated with the first totem pattern. The at least one touchpointdivot may be positioned at a respective known distance from the origin.

To illustrate, reference is now made to FIG. 8, which illustrates areference body 800 affixable to objects tracked by a surgical navigationsystem, in accordance with another example of the present application.The reference body 800 may include a first layer having a first totempattern 822 and an origin 824 of orientation axes 826 similar to thefirst totem pattern 622 and the origin 624 of orientation axes 626illustrated in FIGS. 6A and 6B.

The reference body 800 may also include a plurality of touchpoint marksor divots positioned at known positions relative to the origin 824. Forexample, the reference body 800 may include a first touchpoint 832, asecond touchpoint 834, and a third touchpoint 836. In some examples, theplurality of touchpoints may not be combined with retroreflectivematerials. The plurality of touchpoints may be recessed divots extendingfrom the first layer to the substrate for touch point registration ofthe first totem pattern 822. For example, registration based ontouchpoints at known or pre-configured positions may include operationssuch as: (1) identifying fiducial touchpoints on the reference body 800;(2) detecting touch operations of the fiducial touchpoints with aninstrument that may be tracked by the tracking system 213 (FIG. 2); and(3) generating registration data relating to the position of the trackedinstrument when the tracked instrument “touches” the fiducialtouchpoints on the reference body. Accordingly, the reference body 800may facilitate touchpoint registration operations for determining a poseof the reference body 800 (and the associated object being tracked)and/or registering the reference body 800 in the surgical coordinatespace.

Although the reference bodies described above include a single totempattern, such as the first totem pattern 622 in FIG. 6, in someexamples, a reference body may include two or more totem patterns. Toillustrate, reference is now made to FIG. 9, which illustrates areference body 900 including a plurality of uniquely identifiable totempatterns, in accordance with an example of the present application. Forexample, in addition to a first totem pattern, a first layer of areference body may include additional totem patterns.

The reference body 900 may be a rectangular shaped reference bodyincluding a first layer having the plurality of uniquely identifiabletotem patterns. For ease of exposition, the totem patterns areidentified using numbers 0 to 3, 5, 7, 8, 10 to 13, 15, and 17. Each ofthe totem patterns may include one or more unique identifiable featuredistinguishing that totem pattern from another totem pattern. In someexamples, each of the totem patterns may be non-overlapping with anothertotem pattern. As illustrated in FIG. 9, the first totem pattern(identified with number 0) includes a unique arrangement of blocks thatmay be distinguishable from each of the other totem patterns of thereference body 900.

In some examples, each of the totem patterns may be positioned on thefirst layer at a known position relative to other totem patterns suchthat a combination of the totem patterns is a marker group detectable bythe surgical navigation system 200 (FIG. 2) as a composite totempattern. The totem pattern identified by the number 8, for example, ispositioned on the first layer of reference body 900 at a pre-configuredor known distance from each of the other totem patterns. Accordingly,the surgical navigation system 200 may detect the arrangement of totempatterns of the reference body 900 and may: (1) identify or determinepose information based on each totem pattern individually; or (2)identify or determine pose information based on the combined arrangementof the plurality of totem patterns. That is, each totem pattern may bedetected by the surgical navigation system 200 as an independent totempattern or may be detected and considered by the surgical navigationsystem 200 as a cluster of reference marks providing a composite totempattern. As will be apparent based on the description herein, when thesurgical navigation system 200 considers the cluster of reference marksas a composite totem pattern, the surgical navigation system 200 may insome scenarios also rely on the unique identifiable characteristics ofthe individual totem patterns for determining a pose of the referencebody 900. In some examples, the surgical navigation system 200 may relyon the unique identifiable characteristics when the individual totempatterns may be recognized or deciphered from a captured image of thereference body 900.

The reference body 900 including a combination of two or more arrangedtotem patterns may be desirable in scenarios when the reference body 900may be used in an environment where totem pattern tracking accuracy maybe compromised. Totem pattern tracking accuracy may diminish when anindividual totem pattern may be indiscernible by the tracking system 213of the surgical navigation system 200. For example, the at least onetotem pattern may be indiscernible in an image captured by the trackingsystem 213 when the resolution of the captured image may be insufficientfor resolving unique identifiable feature(s) of the at least one totempattern. The resolution of the captured image may be insufficient forresolving unique identifiable feature(s) of the at least one totempattern when the focal length setting of the tracking system 213 (e.g.,optical imaging device) may cause the totem pattern to appear relativelysmall in the captured image. That is, focal length settings resulting ina wide-angle or “zoomed out” image may cause the totem pattern to appearsmall in the captured image. In another scenario, the at least one totempattern may be indiscernible in an image captured by the tracking system213 when the at least one totem pattern may be out of focus. Forexample, the focus settings of the tracking system 213 (e.g., opticalimaging device) may cause the totem pattern to appear out-of-focus(e.g., blurry). To ameliorate some of the disadvantages of relying uponindividual totem patterns for identifying tracked objects, it may bedesirable to provide reference bodies having two or more totem patternsthat may be detected (1) individually for identifying objects; and/or(2) in combination with other totem patterns based on pre-configured orknown relationships between a plurality of totem patterns. That is, itmay be desirable that the reference body 900 be detectable as anaggregation of single independent totem patterns or as a combination oftotem patterns, where each totem pattern in the combination is spatiallypositioned according to a pre-configured totem pattern layout.

Reference is now made to FIG. 10, which illustrates a flowchart of amethod 1000 of tracking an object in a surgical coordinate space by asurgical navigation system 200 (FIG. 2) including an optical imagingdevice. The tracked object may have a reference body affixed thereto.The reference body may comprise a substrate and a first layer affixed tothe substrate. The first layer may include a plurality of totempatterns. Each totem pattern may have a unique identifiable featuredistinguishing that totem pattern from another totem pattern in theplurality of totem patterns. A position of each totem pattern relativeto other totem patterns may be pre-configured. For example, thereference body 900 of FIG. 9 is an example of a reference body having aplurality of totem patterns, where a position of each totem patternrelative to other totem patterns may be pre-configured or known. In someother examples, relative positions of each totem pattern relative toother totem patterns may be determined during a calibration phase forthe surgical navigation system 200. That is, relative positions of eachtotem pattern relative to other totem patterns may be determined whenthe surgical navigation system 200 is being configured or setup for atarget medical procedure. Once positions of each totem pattern relativeto other totem patterns may be determined, a group of totem patterns mayform a composite totem pattern, as described herein. The tracking system213 (FIG. 2) of the surgical navigation system 200 may include theoptical imaging device.

At operation 1010, the surgical navigation system 200 may capture animage of the tracked object. The image may include image data associatedwith at least one totem pattern. If the surgical navigation system 200captures an image of the tracked object at a short focal length, thecaptured image may include the reference body including a plurality oftotem patterns. For example, the reference body 900 of FIG. 9 mayinclude a plurality of totem patterns. If the totality of totem patternsis captured in the image, the totality of the totem patterns may be acomposite totem pattern. Conversely, if the surgical navigation system200 captures an image of the tracked object at a long focal length, thecaptured image may include fewer number of totem patterns. That is, thecaptured image may not include image data associated with some of thetotem patterns of the reference body 900. Thus, in some examples, thesurgical navigation system 200 may rely on individual totem patterns foridentifying objects or determining pose information.

At operation 1020, the surgical navigation system 200 may determinewhether a unique identifiable feature associated with at least one totempattern is discernible in the captured image. For example, at least onetotem pattern may be indiscernible when the resolution of the capturedimage may be insufficient for resolving the unique identifiable featureof the at least one totem pattern. In another example, the at least onetotem pattern may be indiscernible when the at last one totem patternwithin the captured image may be out of focus.

When the unique identifiable feature of at least one totem pattern isdiscernible, at operation 1030, the surgical navigation system 200 maydetermine a position or an orientation of the tracked object in thesurgical coordinate space based on the at least one totem pattern.

In some examples, the surgical navigation system 200 may include anoptical imaging device with an infrared transmitter and receiver foridentifying reference bodies. The at least one totem pattern that isdiscernible may be included in a reference body similar to the referencebody 700 of FIG. 7. When the infrared transmitter transmits an infraredemission, retroreflective portions exposed via through-holes (e.g.,retroreflective disks) may reflect infrared emissions back to theoptical imaging device and the surgical navigation system 200 maydetermine a position or an orientation of the tracked object based onthe totem pattern and the retroreflective portions detectable via thethree through-holes. That is, the combination of the totem pattern andthe “retroreflective disks” at known positions relative to the originmay provide the surgical navigation system 200 with information fordetermining position and orientation of the reference body in thesurgical coordinate space.

At operation 1040, the surgical navigation system 200 may register theat least one totem pattern associated with the tracked object in thesurgical coordinate space. The surgical navigation system 200 mayperform registration according to any of known registration techniques.

When the unique identifiable feature of at least one totem pattern isindiscernible, at operation 1050, the surgical navigation system 200 maydetermine a position of each totem pattern relative to other totempatterns in the captured image such that a combination of totem patternswithin the captured image is a marker group detectable by the surgicalnavigation system 200 as a composite totem pattern.

If the surgical navigation system 200 captures an image of the entirereference body 900 illustrated in FIG. 9, the surgical navigation system200 may determine that unique identifiable features of the totempatterns may be indiscernible if the captured image is a low resolutionimage and the unique identifiable features of the depicted totempatterns cannot be recognized. In another example, the surgicalnavigation system 200 may determine that unique identifiable features ofthe totem patterns may be indiscernible if the unique identifiablefeatures of the depicted totem patterns are out of focus.

Accordingly, at operation 1050, the surgical navigation system 200 maydetermine that the combination of totem patterns within the referencebody 900 is a composite totem pattern and, thus, determine a position ofeach totem pattern relative to other totem patterns in the capturedimage.

At operation 1060, the surgical navigation system may determine aposition or an orientation of the tracked object in the surgicalcoordinate space based on the composite totem pattern associated withthe tracked object.

At operation 1070, the surgical navigation system 200 may register thecomposite totem pattern associated with the tracked object in thesurgical coordinate space. The surgical navigation system 200 mayperform registration according to any number of known registrationtechniques.

In some examples, when the surgical navigation system 200, at operation1020, may be unable to discern or recognize at least one uniqueidentifiable feature associated with at least one totem pattern so as todistinguish that totem pattern from other totem patterns, the surgicalnavigation system 200 may perform operations for ameliorating theinability to discern unique identifiable features from totem patterns.For instance, the tracking system 213 may adjust a focus setting of theoptical imaging device and, subsequently, the surgical navigation system200 may determine whether a unique identifiable feature may bediscernible in the re-focused image capture.

If focus setting adjustments to the optical imaging device do not remedythe indiscernible totem patterns, the surgical navigation system maycarry out operation 1050, operation 1060, and operation 1070, asdescribed above. In contrast, if focus setting adjustments to theoptical imaging device appear to correct deficiencies in detecting tokenpattern details, the surgical navigation system 200 may utilizeindividual token patterns on their own for registration.

Although the above example operations describe adjusting focus settingswhen attempting to ameliorate inabilities to discern totem patterns fromcaptured images, it may be appreciated that other optical imaging devicesettings may be adjusted for attempting to ameliorate inabilities todiscern totem patterns. For example, shutter speed or aperture settingsmay be adjusted to alter image brightness characteristics that mayaffect discernibility or detectability of token patterns.

As described, it may be desirable to provide one or more referencebodies affixable to objects that may be tracked by surgical navigationsystems, such that the reference bodies may be uniquely identifiable.Once reference bodies (and associated objects on which reference bodiesmay be affixed) are registered in the surgical coordinate space, in someexamples, it may be desirable to associate augmented reality overlayswith a tracked object based on at least one totem pattern or compositetotem pattern and to display the augmented reality overlays on a displayor an augmented reality device to augment a real world view of thetracked object. That is, the at least one totem pattern or compositetotem pattern may be used to anchor a position or orientation of anaugmented realty overlay to captured images. In some examples, augmentedreality overlays may include pre-operative image data associated withthe real world view of the tracked object. Accordingly, augmentedreality overlays may be generated from pre-operative images of a patientand displayed by an augmented reality device such that a user of thataugmented reality device may view the patient (in the real world) alongwith augmented images or information provided by the augmented realityoverlay.

In some examples, a reference body may also include a retroreflectiveportion associated with each of a plurality of totem patterns of thereference body. The respective retroreflective portions may bepositioned at known positions from an origin of orientation axes ofrespective totem patterns and the retroreflective portions may bedetectable by an optical imaging device of the surgical navigationsystem. For example, the surgical navigation system may be configured totransmit electromagnetic emissions (e.g., infrared or visible lightemissions) in a direction of the reference body, and the respectiveretroreflective portions may reflect the electromagnetic emissions backto an optical imaging device of the surgical navigation system. In someexamples, determining a position of a tracked object may includedetermining a position based on reflected light from respectiveretroreflective portions being detected by an optical imaging device.That is, the surgical navigation system may determine a position ororientation of the reference body based on detection of the totempattern and/or retroreflective portion(s) of the reference body.

In some examples, the reference body may include a retroreflectiveportion having three or more retroreflective markers, each of the threeor more retroreflective markers positioned at known positions from theorigin position of orientation axes associated with the respective totempatterns. In some examples, determining the position or the orientationof a tracked object in a surgical coordinate space may includedetermining a position or orientation of the reference body using touchpoint registration based on touch points at the three or moreretroreflective markers of the respective totem patterns.

Reference is now made to FIGS. 11 and 12, which illustrates exampletotem patterns, in accordance with examples of the present application.As illustrated in FIG. 11, each of the totem patterns may bedistinguishable from another totem pattern based on unique features. Forexample, unique features may include different text (e.g., “1”, “2”, or“3”). In other examples, unique features may include differentconfiguration of circular or curved line shapes. In some examples, if asurgical navigation system is configured to detect colors, uniquefeatures may be differentiated based on colors. As illustrated in FIG.12, each of the totem patterns may be distinguishable from another totempattern based on graphical designs. It will be appreciated thatreference bodies described herein may include totem patterns havingfeatures of quick response (QR) codes, bar codes, or any symbols havingsufficiently identifiable features that may be used to distinguish thattotem pattern from other totem patterns.

As described herein, surgical navigation systems may determine positionand/or orientation of tracked objects by detecting reference bodiesaffixed to tracked objects. In some examples, surgical navigationsystems may not require continuous, real-time detection of the referencebodies described herein, but may be configured to update reference bodypositions and/or orientations when a detected line of sight may beestablished.

In some examples, optical imaging devices of surgical navigation systemsmay be associated with a first imaging modality. The first imagingmodality may be a video imaging device. For example, the video imagingdevice may optically capture images of reference bodies (e.g., totempatterns and/or retroreflective disks). Further, the retroreflectiveportion or a substrate may include a contrast material detectable by asecond imaging device associated with a second imaging modality. Forinstance, the second imaging modality may include one of magneticresonance imaging or computed tomography imaging. Accordingly, examplereference bodies described herein may be configured for multi-modalityregistration methods that may be used to register images acquired bydifferent scanning or sensor technologies.

Certain adaptations and modifications of the described embodiments canbe made. Therefore, the above discussed embodiments are considered to beillustrative and not restrictive.

What is claimed is:
 1. A method of tracking an object in a surgicalcoordinate space by a surgical navigation system including an opticalimaging device, the tracked object having a reference body affixedthereto, the reference body comprising a substrate and a first layeraffixed to the substrate, the first layer including a plurality of totempatterns, each totem pattern having a unique identifiable featuredistinguishing that totem pattern from another totem pattern in theplurality of totem patterns, the method comprising: capturing an imageof the tracked object, the image including image data associated with atleast one totem pattern; determining whether a unique identifiablefeature associated with at least one totem pattern is discernible in theimage; when the unique identifiable feature associated with at least onetotem pattern is discernible: determining a position or an orientationof the tracked object in the surgical coordinate space based on the atleast one totem pattern; and registering the at least one totem patternassociated with the tracked object in the surgical coordinate space; andwhen the unique identifiable feature associated with at least one totempattern is indiscernible: determining a position of each totem patternrelative to other totem patterns in the captured image such that acombination of totem patterns within the captured image is a markergroup detectable by the surgical navigation system as a composite totempattern; determining a position or an orientation of the tracked objectin the surgical coordinate space based on the composite totem patternassociated with the tracked object; and registering the composite totempattern associated with the tracked object in the surgical coordinatespace.
 2. The method of claim 1, wherein the at least one totem patternis indiscernible when resolution of the captured image is insufficientfor resolving the unique identifiable feature of the at least one totempattern.
 3. The method of claim 1, wherein the at least one totempattern is indiscernible when the at least one totem pattern within thecaptured image is out of focus.
 4. The method of claim 1, wherein whenthe at least one totem pattern is indiscernible, prior to determiningthe position of each totem pattern relative to other totem patterns inthe captured image, the method further comprising: adjusting focalsetting of the optical imaging device; and when the unique identifiablefeature of the at least one totem pattern continues to be indiscernible:determining the position of each totem pattern relative to other totempatterns in the captured image such that the combination of totempatterns within the captured image is the marker group detectable by thesurgical navigation system as the composite totem pattern; anddetermining the position or the orientation of the tracked object in thesurgical coordinate space based on the composite totem patternassociated with the tracked object.
 5. The method of claim 1, furthercomprising: associating an augmented reality overlay with the trackedobject based on the at least one totem pattern or the composite totempattern; and displaying the augmented reality overlay on a display or anaugmented reality device to augment a real world view of the trackedobject.
 6. The method of claim 5, wherein the augmented reality overlayis pre-operative image data associated with the real world view of thetracked object.
 7. The method of claim 1, wherein the reference bodyfurther includes a retroreflective portion associated with each of thetotem patterns, the retroreflective portion positioned at a knownposition from an origin of orientation axes associated with respectivetotem patterns such that the retroreflective portion is detectable bythe optical imaging device, and wherein determining the position of thetracked object includes determining the position based onelectromagnetic emission or reflection from respective retroreflectiveportions being detected by the optical imaging device.
 8. The method ofclaim 7, wherein the retroreflective portion associated with each of thetotem patterns includes three or more retroreflective markers, each ofthe three or more retroreflective markers positioned at known positionsfrom the origin position of orientation axes associated with therespective totem patterns, and wherein determining the orientation ofthe tracked object includes determining the orientation based onelectromagnetic emission incident on the three or more retroreflectivemarkers associated with each of the totem patterns being detected by theoptical imaging device.
 9. The method of claim 1, wherein the referencebody further includes touchpoint divots associated with each of thetotem patterns, each of the touchpoint divots positioned at knownpositions from the origin position of orientation axes associated withthe respective totem patterns, and wherein determining the position orthe orientation of the tracked object in the surgical coordinate spaceincludes determining the position or the orientation using touch pointregistration based on touch points at the touchpoint divots of therespective totem patterns.
 10. A surgical navigation system to track anobject in a surgical coordinate space, the tracked object having areference body affixed thereto, the reference body comprising asubstrate and a first layer affixed to the substrate, the first layerincluding a plurality of totem patterns, each totem pattern having aunique identifiable feature distinguishing that totem pattern fromanother totem pattern in the plurality of totem patterns, the surgicalnavigation system comprising: a processor; an optical imaging devicecoupled to the processor; and a memory coupled to the processor andstoring processor-readable instructions that, when executed, cause theprocessor to perform the method according to claim 1.